JP5977531B2 - Method for manufacturing friction modifier - Google Patents

Description

  The present invention relates to a brake friction material and clutch facing used in automobiles, railway vehicles, industrial machines, and the like, and more particularly to a friction adjusting material blended in the friction material.

Friction materials used for brakes such as disc brakes and drum brakes used in automobiles, etc., or clutches, friction adjusting materials that adjust the friction performance, and fiber base materials that reinforce, They are made of a material such as a binder that integrates them to give strength. Since the friction material frictionally engages with its counterpart material and plays a role of changing kinetic energy into heat energy, excellent heat resistance, wear resistance, and a high friction coefficient are required.
There are inorganic and organic friction modifiers and solid lubricants as materials for adjusting the friction characteristics of the friction material, but it is difficult to satisfy all the requirements with one type, so usually there are two or more types. Used in combination.
Examples of the friction modifier include inorganic friction modifiers such as alumina, silica, magnesia, zirconia, copper, aluminum, and zinc, and organic friction modifiers such as rubber dust and cashew dust.
Examples of solid lubricants include graphite, molybdenum disulfide, and polytetrafluoroethylene, which are used as powders or thin films to prevent damage to the surface of the relatively moving material and to reduce friction and wear. The

  Cashew dust, one of the organic friction modifiers, is a polymer of cashew oil (sometimes called cashew nut shell liquid) and melts during friction engagement to form a smooth lubricating coating on the surface of the friction material. It has the effect of improving and stabilizing the friction coefficient of the friction material, thereby reducing the friction and extending the life of the friction material. On the other hand, cashew dust is considered to be one factor of the fade phenomenon because it begins to thermally decompose at 250 to 300 ° C.

  In patent document 1, in order to improve the heat resistance of cashew dust, a method of modifying with a boron or phosphorus compound is disclosed. Improvement of heat resistance of cashew dust by boron or phosphorus compounds leads to improvement of the fade characteristics of the friction material, and a sufficiently high friction coefficient can be ensured even at high loads.

JP 09-48967 A

However, the low heat resistance of cashew dust can be improved by modification with boron or a phosphorus compound as in Patent Document 1, while these have improved heat resistance by protecting the phenolic hydroxyl group. The amount was limited to the range of 2 to 10% by weight, and the effect of improving heat resistance was limited. In addition, since boron is an environmentally hazardous substance, the use of boron compounds has room for improvement as a friction modifier, for example, there are restrictions on environmental considerations.
Therefore, the first object of the present invention is to improve the heat resistance of cashew dust, thereby suppressing the fade phenomenon of the friction material containing the friction modifier and improving the wear resistance at high temperature. To do.
A second object of the present invention is to provide a friction material having the above-mentioned properties and having the above-mentioned excellent performance, which is blended with an environment-friendly friction modifier.

  As a result of earnest study to achieve the above object, the present inventor can obtain a friction modifier having high heat resistance by mixing and heat-curing cashew oil and polycarbosilane. The headline and the present invention were completed.

That is, the present invention relates to the following (1) to (5).
(1) A friction modifier comprising a cashew oil and a silicon-containing polymer, the friction modifier being obtained by heat-curing and then pulverizing a mixture of the cashew oil, the silicon-containing polymer and a curing agent.
(2) The silicon-containing polymer according to (1), wherein the silicon-containing polymer is one or more compounds selected from the group consisting of polycarbosilane, polyorganoborosilazane, polyborosiloxane, polycarbosilazane, and perhydropolysilazane. Friction modifier.
(3) The friction modifier according to (1) or (2) above, containing 5 to 30% by mass of the silicon-containing polymer.
(4) A friction material including a fiber base material, a friction modifier, and a binder, and the friction containing the friction modifier according to any one of (1) to (3) as the friction modifier. Wood.
(5) A method for producing a friction modifier, comprising a step of heat-curing a mixture of cashew oil, a silicon-containing polymer, and a curing agent, and then pulverizing the mixture.

  The friction preparation material of the present invention is a friction modifier having high heat resistance obtained by heat-curing a mixture of cashew oil, polycarbosilane and a curing agent, and the friction material to which the friction modifier is added, A fade phenomenon and an increase in wear at high temperatures can be suppressed.

Hereinafter, the present invention will be described in detail.
The cashew oil used in the present invention is an oil (liquid) extracted from a cashew nut shell containing cardanol, cardol, methyl cardol or anacardic acid as a component, and its main component is cardanol. Cardanol is a phenol derivative having a linear or branched aliphatic hydrocarbon group having 10 to 30 carbon atoms in the m-position, and the hydrocarbon group contains an unsaturated bond composed of alkenyl, diene or triene.
When cashew oil is used in the present invention, it can be used in any form of monomer (oil), oligomer, or modified cashew oil.

The organometallic compound to be mixed with cashew oil of the present invention is preferably a silicon-containing polymer. Specific examples of the silicon-containing polymer include thermally decomposable polymers such as polycarbosilane, polyorganoborosilazane, polyborosiloxane, polycarbosilazane, and perhydropolysilazane.
The blending ratio of the silicon-containing polymer to the cashew oil in the friction modifier is preferably 5 to 30% by mass, and more preferably 10 to 30% by mass. If it is this range, the friction modifier which has heat resistance and abrasion resistance can be obtained.

  Considering the price and availability, polycarbosilane is preferable among the silicon-containing polymers as the binder (binder) used in the present invention. The type of polycarbosilane used in the present invention is not particularly limited. For example, it is an organosilicon polymer containing at least 30% by mass or more of a repeating unit represented by the following general formula I, general formula II or general formula III. .

(In the formula, R ¹ represents a hydrogen atom, an alkyl group or a hydroxyl group, R ² represents an alkyl group, a phenyl group or a halogen atom, and n represents an integer. R ¹ and R ² may be the same.)
The polycarbosilane may be a homopolymer, a copolymer, a block or a graft, or a blend thereof. The number average molecular weight of the polycarbosilane in the present invention is usually 500 to 10,000.

The friction modifier is manufactured by mixing cashew oil (including oligomers), a silicon-containing polymer and a curing agent in a reaction vessel equipped with a stirrer, and then heat-curing, cooling, and pulverizing the friction modifier. Can be obtained.
More preferably, cashew oil (including oligomers) and silicon-containing polymer are mixed with sufficient stirring in the presence of a solvent, and then cured by heat treatment (crosslinking polymerization) with the addition of a curing agent and a catalyst as necessary. The friction modifier can be obtained by cooling and grinding.
More preferably, cashew oil (including oligomers) and silicon-containing polymer are mixed in a solution state at 10-30 ° C. for 1-6 hours with sufficient stirring, and then, together with a curing agent and, if necessary, a catalyst. After stirring and mixing for 30 minutes, gelation is performed by allowing to stand at 10 to 30 ° C. for 12 to 36 hours. The obtained gel-like mixture is cured by heat treatment (crosslinking polymerization) at 150 to 250 ° C. for 1 to 10 hours, and a friction modifier can be obtained by cooling and pulverization.

  Here, the particle size of the pulverized friction modifier is not particularly limited and can be determined at the discretion of a person skilled in the art according to characteristics required for the friction material. In order to avoid deterioration of the property, the thickness is preferably 10 to 1000 μm, more preferably about 100 to 500 μm. The average particle diameter is a value measured by a laser diffraction particle size distribution meter.

Compared to the method of manufacturing a friction modifier that mixes powders of cashew polymer and silicon-containing polymer in a polymer state, the method of manufacturing the friction modifier described above is a uniform mixing of cashew oil and silicon-containing polymer using a solvent. There is a feature in the point to do. After thoroughly mixing and heat-curing, it is considered that a friction modifier can be obtained in which cashew dust (polycondensate of cashew oil) and silicon-containing polymer are uniformly combined in situ at the molecular level. It is done. Moreover, the friction modifier of arbitrary hardness can be obtained by changing the compounding ratio of cashew oil and a silicon-containing polymer.
Polycarbosilane has the property of being ceramicized by heating and not lose weight by heating. Therefore, if polycarbosilane is uniformly dispersed at the molecular level in cashew dust, it is presumed that the effects of the above-described properties of polycarbosilane in the friction modifier are exhibited evenly. When this friction modifier is added to the friction material, it is considered that the fade effect generated at high temperature is suppressed and the effect of improving the wear resistance is increased.

In the above reaction, the reaction solvent is not particularly limited, but o-xylene, methyl ethyl ketone, tetrahydrofuran, dioxane, methyl cellosolve, acetonitrile, ethyl acetate or toluene, or a mixture thereof can be used, and o-xylene is particularly preferable.
Moreover, what is necessary is just to determine the usage-amount of a reaction solvent suitably.

Examples of the curing agent for the friction modifier include aldehyde compounds, amine compounds (for example, hexamethylenetetramine), and epoxy compounds (for example, epichlorohydrin), among which aldehyde compounds are preferable.
Examples of the aldehyde compound include formaldehyde, paraformaldehyde, trioxane, acetaldehyde, propionaldehyde, polyoxymethylene, chloral, glyoxal, n-butyraldehyde, caproaldehyde, allylaldehyde, crotonaldehyde, acrolein, tetraoxymethylene, furfural, benzaldehyde, Phenylacetaldehyde, o-tolualdehyde, salicylaldehyde and the like can be mentioned, among which furfural, paraformaldehyde and the like are preferable.

Depending on the type of curing agent, it is necessary to add a catalyst as appropriate, and examples of the catalyst include amine-based or acidic curing catalysts, and acidic curing catalysts are preferred. As an acidic curing catalyst, mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid, alkyl esters thereof, organic acids such as oxalic acid, paratoluenesulfonic acid, paraphenolsulfonic acid and the like can be used. The alkyl esters are preferably, for example, alkyl sulfates such as dimethyl sulfate and diethyl sulfate.
When furfural is used as the curing agent, it is particularly preferable to add dimethyl sulfate as a catalyst.

As a specific aspect of the production method of the present invention, cashew oil and 5 to 30% by mass of polycarbosilane based on cashew oil are mixed using o-xylene as a solvent, and then the solvent is removed, and a curing agent is used. After adding furfural as a catalyst and dimethylsulfuric acid as a catalyst, the friction modifier is cured by heating to advance the polymerization reaction.
Further, hexamethylenetetramine may be used as the curing agent instead of furfural. In this case, it is not necessary to add a catalyst, and the heat curing may be performed as it is.

The friction modifier obtained in the present invention can be used as a compounding material for a friction material. In blending the friction material, a commonly used blending material is used. Examples thereof include a fiber base material; a binding material; a friction adjusting material called an abrasive, a filler, a solid lubricant, and the like.
As the fiber base material, organic fiber, inorganic fiber, and metal fiber are used. Examples of organic fibers include aromatic polyamide (aramid) fibers and flame-resistant acrylic fibers. Examples of inorganic fibers include ceramic fibers such as potassium titanate fibers and alumina fibers, biosoluble inorganic fibers, glass fibers, and carbon fibers. Fibers, rock wool, and the like are used, and as the metal fibers, for example, copper fibers and steel fibers are used.

As the binder, for example, a thermosetting resin such as phenol resin (including various modified phenol resins such as straight phenol resin and rubber), melamine resin, epoxy resin, and polyimide resin is used.
As friction modifiers, inorganic fillers such as barium sulfate, calcium carbonate, calcium hydroxide, vermiculite, mica, abrasives such as alumina, silica, magnesia, zirconia, zirconium silicate, chromium oxide, copper, aluminum, bronze, Metal fillers such as zinc, various rubber powders (rubber dust, tire powder, etc.), organic fillers such as cashew dust and melamine dust, and solid lubricants such as graphite (graphite) and molybdenum disulfide are used.
These friction modifiers and the friction modifier of the present invention can be used in combination without any problem, and the mixing ratio can be determined at the discretion of those skilled in the art.

The mixing ratio of the various compounding materials is preferably 15 to 55% by mass of the fiber base material based on the entire friction material, 10 to 60% by mass of the friction modifier, and 5 to 35% by mass of the binder. The adjusting material is preferably 1 to 15% by mass of the entire friction material.
Of the above mixing ratios, the fiber base material is more preferably 25 to 45% by mass of the friction material, 20 to 50% by mass of the friction modifier, and 15 to 25% by mass of the binder, and the friction modifier of the present invention. Is more preferably 5 to 15% by mass of the entire friction material.

The friction material can be manufactured by a well-known manufacturing process. For example, the friction material can be manufactured through processes such as preforming, thermoforming, heating, and polishing.
The general steps in manufacturing a disc brake friction pad are as follows.
(A) forming a pressure plate into a predetermined shape by a sheet metal press;
(B) A step of subjecting the pressure plate to a degreasing treatment and a primer treatment,
(C) A raw material obtained by blending a fiber base material such as an organic fiber, an inorganic fiber, or a metal fiber and a powder raw material such as a friction modifier, a friction modifier of the present invention, and a binder, and sufficiently homogenizing by stirring. , A step of forming a preform by molding at a predetermined pressure at room temperature,
(D) a thermoforming process in which the preform and the pressure plate coated with an adhesive are fixed together by applying a predetermined temperature and pressure;
(E) A step of after-curing and finally finishing.
The friction material in the present invention can also be manufactured by such a process.

EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples.
(Preparation of friction modifier A)
In a 2000 mL flask, 500 g of cashew oil and 25 g of polycarbosilane (manufactured by Ube Industries, Ltd.) were taken and mixed with 500 g of o-xylene. The solution was stirred at room temperature for 1 hour, and the cashew oil and polycarbosilane were mixed well, then vacuum dried at 170 ° C. for 10 hours to remove the solvent o-xylene, and the mixture of cashew oil and polycarbosilane was recovered. did.
Next, the obtained mixture is mixed with 160 g of furfural as a curing agent, and further 13.5 g of dimethylsulfuric acid catalyst is added, mixed by stirring for 10 minutes, then placed in a vat and allowed to stand at room temperature for 24 hours. Gelled.
The gel-like mixture was cured by heat polymerization in an oven at 200 ° C. for 5 hours, followed by cooling and pulverization processes to obtain a friction modifier A having an average particle size of 250 μm.

(Preparation of friction modifier B)
In a 2000 mL flask, 500 g of cashew oil and 50 g of polycarbosilane were taken and mixed with 500 g of o-xylene. The solution was stirred at room temperature for 1 hour, and the cashew oil and polycarbosilane were mixed well, then vacuum dried at 170 ° C. for 10 hours to remove the solvent o-xylene, and the mixture of cashew oil and polycarbosilane was recovered. did.
Next, the obtained mixture is mixed with 160 g of furfural as a curing agent, and further 13.5 g of dimethylsulfuric acid catalyst is added, mixed by stirring for 10 minutes, then placed in a vat and allowed to stand at room temperature for 24 hours. Gelled.
The gel-like mixture was cured by heat polymerization in an oven at 200 ° C. for 5 hours, followed by cooling and pulverization processes to obtain a friction modifier B having an average particle size of 250 μm.

(Preparation of friction modifier C)
In a 2000 mL flask, 500 g of cashew oil and 150 g of polycarbosilane were taken and mixed with 500 g of o-xylene. The solution was stirred at room temperature for 1 hour, and the cashew oil and polycarbosilane were mixed well, then vacuum dried at 170 ° C. for 10 hours to remove the solvent o-xylene, and the mixture of cashew oil and polycarbosilane was recovered. did.
Next, the obtained mixture is mixed with 160 g of furfural as a curing agent, and further 13.5 g of dimethylsulfuric acid catalyst is added, mixed by stirring for 10 minutes, then placed in a vat and allowed to stand at room temperature for 24 hours. Gelled.
The gel-like mixture was cured by heat polymerization in an oven at 200 ° C. for 5 hours, followed by cooling and pulverization processes to obtain a friction modifier C having an average particle size of 250 μm.

(Preparation of friction modifier D)
500 g of cashew oil was taken into a 2000 mL flask, and 160 g of furfural as a curing agent and 13.5 g of dimethyl sulfate as a catalyst were mixed with stirring for 10 minutes. Thereafter, the gel was formed by opening in a vat and allowing to stand at room temperature for 24 hours.
The gel-like mixture was cured by heat polymerization in an oven at 200 ° C. for 5 hours, followed by cooling and pulverization processes to obtain a friction modifier D having an average particle size of 250 μm.
Table 1 shows the blending ratio of polycarbosilane to cashew oil in the friction modifiers A to D.

(Examples 1 to 3 and Comparative Example 1)
(Thermogravimetric analysis)
The thermal stability test of the friction modifiers A to D obtained by the above method was performed by thermogravimetric analysis (TGA) using a differential thermothermal gravimetric simultaneous measurement apparatus EXSTAR TG / DTA6300 manufactured by Seiko Instruments Inc. went. The measurement was performed at a temperature rising rate of 10 ° C./min up to a temperature range of 30 to 1000 ° C. Each weight retention rate (%) was determined from the thermal weight loss at 300 ° C., 400 ° C., and 500 ° C. based on the weight of the friction modifier before measurement. The results are shown in the friction modifier evaluation results in Table 2.

(Production of friction material)
Friction modifiers A to D obtained by the above method and various compounding materials were mixed with a mixer at a ratio described in the friction material compounding in Table 2 and then charged into a pre-molding die and pressurized at 30 MPa to prepare. Molding was performed. These operations were performed at room temperature. Next, the preform and a pressure plate pre-applied with an adhesive were set in a thermoforming mold and subjected to heat and pressure molding at 150 ° C. and 50 MPa for 5 minutes. The obtained thermoformed body was heat-treated at 250 ° C. for 3 hours to obtain friction materials A to D.

(Fade test)
A 13 mm × 15 mm × 35 mm test piece was cut out from the friction materials A to D obtained by the above method, and a friction test was performed using a friction analyzer friction tester manufactured by Sakai Engineering Co., Ltd. according to JASO-C406-82. The minimum friction coefficient and friction material wear amount of the first fade were measured. The results are shown in the friction material evaluation results in Table 2.

From Table 2, it can be seen that the weight retention of the friction modifiers A to C is higher than that of the friction modifier D that does not contain polycarbosilane at 400 ° C. to 500 ° C. at which the fading phenomenon is likely to occur. From this, it can be seen that by combining cashew oil and polycarbosilane, heat loss of the friction modifier is suppressed and heat resistance is improved.
Moreover, in the friction material which mix | blended friction modifiers A-C, the minimum friction coefficient at the time of a 1st fade improved and the friction material wear amount decreased. This is considered due to the improvement in heat resistance of the friction modifier.

The present invention provides a friction modifier with improved heat resistance without using environmentally hazardous substances. Along with this improvement in heat resistance, the effect of suppressing fade and improving the amount of wear of the friction material including the friction modifier is greatly recognized.
For these reasons, it can be suitably used for disk pads, brake linings, clutch facings, etc. for automobiles, railway vehicles, and various industrial machines.

Claims (2)

Cashew oil, and heat-curing the silicon-containing polymer, and a mixture of curing agent and then looking contains a step of pulverizing, the silicon-containing polymer is polycarbosilane, polyorganosiloxanes rags silazane, polyborosiloxane, polycarbosilazane, perhydropolysilazane A method for producing a friction modifier, which is one or more compounds selected from the group consisting of :   The manufacturing method of the friction modifier of Claim 1 which contains the said silicon containing polymer 5-30 mass%.